An automatic wire connection device for connecting a wire electrode of a wire electric discharge machining device performs a process of improving a connection performance, by annealing and straightening a wire having a bending tendency. For example, conventionally, Patent Literature 1 proposes a technique of heating and annealing a wire electrode to lessen the bending tendency of a wire electrode so as to improve the machining capability of a wire electric discharge machining device. Patent Literature 2 discloses a technique of measuring heat stretch of a wire electrode and using the measured heat stretch so as to control the temperature of the wire electrode to a predetermined temperature during an annealing process. Patent Literature 3 describes a method of estimating the temperature of a wire electrode that is being machined from a current value and a resistance value. Furthermore, as shown in FIG. 51 and FIG. 53 of Non Patent Literature 1, it is known that mechanical properties of brass, which is a material often used as the material of a wire electrode of an electric discharge machining device, changes depending on a temperature.